Current methods for producing hydroquinone involve oxidation of aniline with manganese dioxide to quinone followed by reduction with iron dust to hydroquinone or oxidation of diisopropyl benzene to the dihydroperoxide followed by cleavage with acid to hydroquinone.
In the first method large quantities of manganese dioxide are converted to manganese sulfate and, therefore, in order to have a commercially feasible process it is necessary to have a market for the manganese sulfate produced.
In the second method it is necessary to start with highly pure para-diisopropyl benzene and to separate the dihydroperoxide from the monohydroperoxide which is also produced as a by-product. Procedures are available for this separation but they are costly and time-consuming operations. Furthermore, the acid catalyzed conversion of the dihydroperoxide to hydroquinone also produces relatively large amounts of high boiling undesirable by-products.
The instant process not only avoids problems associated with the prior art processes but also has a number of advantages which are distinctly characteristic of the process of the instant invention. The advantages of the instant invention are that readily available starting materials are employed and useful by-products are formed. The organic hydroperoxides are either available commercially or can be prepared readily by air oxidation of the corresponding hydrocarbon. For example, tertiary butyl hydroperoxide is a commercially available product which in the process is reduced to tertiary butyl alcohol and this compound is turn can be used as a gasoline additive or can be dehydrated to isobutylene which is a useful monomer. Cyclohexane can be oxidized to the cyclohexyl hydroperoxide which in the process is reduced to cyclohexanol, this in turn when dehydrated gives cyclohexene which is a starting material used in the invention. Alternatively the cyclohexanol can be used as a precursor for adipic acid production. If ethylbenzene is oxidized to the hydroperoxide it in turn is reduced to the alcohol which when dehydrated produces styrene. If cumene hydroperoxide is employed the alcohol reduction product when dehydrated gives the useful product alphamethylstyrene.
The monocarboxylic acids utilized in the process can be recovered and recycled to the process as will be shown hereinafter. Thus, if acetic acid which is available commercially is employed it can be recovered readily and recycled.
The cyclohexene can either be a recycled product as pointed out or is available by the dehydrogenation of cyclohexane.
Finally, it has been found that essentially no high boiling point by-product compounds are formed by the process of this invention.